Tool having multi-speed compound planetary transmission

ABSTRACT

A tool having a housing assembly, which defines a handle, a motor assembly, a trigger assembly, a spindle and a transmission assembly. The motor assembly is received in the housing assembly and has an output shaft. The trigger assembly is coupled to the housing assembly and is configured for use in actuating the motor assembly. The transmission assembly transmits rotary power between the output shaft of the motor assembly and the spindle. The transmission assembly includes a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier. The planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.

INTRODUCTION

The present invention generally relates to a tool that has a multi-speed compound planetary transmission.

Modernly, manufacturers of power tools have introduced power tools that have variable speed motors in an attempt to permit the users of these tools with sufficient control over the output speed of the tool so as to permit them to perform diverse operations without resort to additional, specialized tools. Many of the tools that are commercially available include a three-stage, two-speed transmission that permits even greater control over speeds of these tools.

Typically available transmission arrangements have lacked a transmission arrangement that could produce a wide range of output speeds and torques that would permit the tool to perform diverse operations such as drilling holes with a large diameter hole saw, installing drywall screws or large diameter lag screws, and performing high-speed drilling operations. The single or dual speed transmissions that were generally employed in these tools typically did not have sufficient speed reducing capacity to permit these transmissions to be diversely employed as configuring these tools for high torque operations tended to impair their high speed performance. Furthermore, the rechargeable batteries that were employed in many of the early cordless rotary power tools were not well suited for use in low-speed, high torque operations due to the amount of energy that is consumed and the rate with which the energy is consumed by the power tool during such operations. Consequently, consumers were often forced to purchase two different rotary power tools, a medium-duty tool for “standard” applications such as drilling and fastening, and a heavy-duty tool having a low-speed, high torque output for more demanding tasks.

With the advent of the modern high capacity, high voltage battery, it is now possible to meet the energy demands of a power tool that is used in low-speed, high torque operations. There remains, however, a need in the art for a power tool transmission having a relatively large range in its speed reducing capacity.

SUMMARY

This section provides a general summary of some aspects of the present disclosure and is not a comprehensive listing or detailing of either the full scope of the disclosure or all of the features described therein.

The present teachings provide a tool having a housing assembly, a motor assembly, a trigger assembly, a spindle and a transmission assembly. The housing assembly defines a handle. The motor assembly is received in the housing assembly and has an output shaft. The trigger assembly is coupled to the housing assembly and is configured for use in actuating the motor assembly. The transmission assembly transmits rotary power between the output shaft of the motor assembly and the spindle.

In one form, the present teachings provide that the transmission assembly includes a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier. The planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.

In another form, the present teachings provide that the transmission assembly includes a gearset portion with a planet carrier, an input sun gear, and at least one compound planet gear supported for rotation by the planet carrier. The planet carrier is an output member of the gearset portion. Each compound planet gear has first and second planet gears that are coupled to one another for common rotation. The first planet gear has a pitch diameter that is different from a pitch diameter of the second planet gear. The gearset portion is operable in a first mode which provides a first gear reduction ratio and a second mode that provides a second gear reduction ratio that is different than the first gear reduction ratio. At least one intermediate gear reduction is provided within an axial length of the planet carrier when the gearset portion is operated in the second mode.

In still another form, the present teachings provide that the transmission assembly includes a gearset portion with a planet carrier, an input sun gear, a compound sun gear, a first planet gear, a second planet gear, a third planet gear, and a plurality of ring gears. The compound sun gear includes a first intermediate sun gear and a second intermediate sun gear that are coupled to one another for common rotation. The first, second and third planet gears are rotatably disposed on the planet carrier. The second planet gear is coupled to the first planet gear for rotation therewith. The first planet gear is meshingly engaged with the input sun gear. The second planet gear is meshingly engaged with the first intermediate sun gear. The third planet gear is meshingly engaged with the second intermediate sun gear. The plurality of ring gears include a first ring gear, which is meshingly engaged to one of the first, second and third planet gears, and a second ring gear that is meshingly engaged to a different one of the first, second and third planet gears. The gearset portion is operable in a first mode in which the first ring gear is maintained in a non-rotating condition relative to the housing assembly and the second ring gear is rotatable relative to the housing assembly. The gearset portion is operable in a second mode in which the second ring gear is maintained in a non-rotating condition relative to the housing assembly and the first ring gear is rotatable relative to the housing assembly.

In yet another form, the present teachings provide that the transmission assembly includes a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier. The planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application and/or uses in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. The drawings are illustrative of selected teachings of the present disclosure and do not illustrate all possible implementations. Similar or identical elements are given consistent identifying numerals throughout the various figures.

FIG. 1 is a side elevation view of an exemplary tool constructed in accordance with the teachings of the present disclosure;

FIG. 2 is an exploded perspective view of the tool of FIG. 1;

FIG. 3 is a longitudinal section view of a portion of the tool of FIG. 1;

FIG. 4 is an enlarged portion of FIG. 3, illustrating a first gearset portion operating in a fourth mode;

FIG. 5 is a view similar to that of FIG. 4 but depicting the first gearset portion operating in a second mode;

FIG. 6 is a view similar to that of FIG. 4 but depicting the first gearset portion operating in a first mode;

FIG. 7 is a longitudinal section view of a portion of another exemplary tool constructed in accordance with the teachings of the present disclosure;

FIGS. 8, 9 and 10 are longitudinal section views of a portion of the tool of FIG. 7, depicting a gearset portion of the tool as operating in first, second and fourth modes, respectively;

FIG. 11 is a longitudinal section view of a portion of another exemplary tool constructed in accordance with the teachings of the present disclosure;

FIGS. 12, 13, 14, 15, 16 and 17 are longitudinal section views of a portion of the tool of FIG. 11, depicting a gearset portion of the tool as operating in sixth, fifth, fourth, third, second and first modes, respectively;

FIG. 18 is a longitudinal section view of a portion of another exemplary tool constructed in accordance with the teachings of the present disclosure;

FIG. 19 is a longitudinal section view of a portion of another exemplary tool constructed in accordance with the teachings of the present disclosure;

FIGS. 20, 21 and 22 are longitudinal section views of a portion of the tool of FIG. 19, depicting a gearset portion of the tool as operating in first, second and third modes, respectively; and

FIG. 23 is a longitudinal section view of a portion of another exemplary tool constructed in accordance with the teachings of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

With reference to FIGS. 1 and 2, an exemplary tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10. The tool 10 can include a housing assembly 12, a motor assembly 14, a trigger assembly 16, a transmission assembly 18, a clutch assembly 20 and an output spindle 22.

The housing assembly 12 can comprise a pair of handle housing shells 30 and a gear case 32 that can be removably coupled to the handle housing shells 30 via a plurality of threaded fasteners (not shown). The handle housing shells 30 can cooperate to define a handle 36, a trigger mount 38, and a cavity 40 into which the motor assembly 14 can be received.

The motor assembly 14 and the trigger assembly 16 can be conventional in their construction and operation. In brief, the motor assembly 14 can include an output shaft 46 that can provide a rotary input (torque) to the transmission assembly 18, while the trigger assembly 16 can be mounted to the trigger mount 38 and employed to selectively couple the motor assembly 14 to a source of electrical power, such as a battery pack 48. In the example provided, the trigger assembly 16 includes a trigger 50, a trigger switch 52, and a reversible variable speed controller 54, but it will be appreciated that various other types of trigger assemblies could be substituted for the particular trigger assembly that is shown in the drawings and described herein.

The transmission assembly 18 can be configured to transmit rotary power between the motor assembly 14 and the output spindle 22 and can include a reduction gearset 60 and a speed change mechanism 62.

With reference to FIGS. 2 through 4, the reduction gearset 60 can comprise a first planetary stage or gearset portion 70, which receives rotary power from the motor assembly 14, and a second planetary stage or gearset portion 72 that receives rotary power from the first gearset portion 70 and transmits rotary power to the output spindle 22.

The first gearset portion 70 can comprise a first or output planet carrier 80, a first or input sun gear 82, a second sun gear 84, a third sun gear 86, a first planet gear 88, a second planet gear 90, a third planet gear 92, a fourth planet gear 94, a first ring gear 96, a second ring gear 98, and a third ring gear 100.

The first planet carrier 80 can comprise a carrier body 104 and a plurality of carrier pins 106. In the example provided, the carrier body 104 comprises a rear plate member 110 and a front plate member 112, and the opposite ends of the carrier pins 106 can be fixedly mounted to the rear and front plate members 110 and 112 to axially space the rear plate member 110 apart from the front plate member 112. The first, second, third and fourth planet gears 88, 90, 92 and 94 can be rotatably mounted on the carrier pins 106. In the example provided, one of each of the first, second, third and fourth planet gears 88, 90, 92 and 94 is rotatably received on each of the carrier pins 106.

The first sun gear 82 can be coupled to the output shaft 46 of the motor assembly 14 for rotation therewith. Teeth of the first sun gear 82 can be meshingly engaged to teeth of the first planet gear 88, which in turn can mesh with teeth of the first ring gear 96. The second sun gear 84 can be rotatable independently of the output shaft 46, the first sun gear 82 and/or the first planet carrier 80. In the example provided, the second sun gear 84 is separate and axially offset from the first sun gear 82 and is maintained in a position that is concentric about a longitudinal axis of the first gearset portion 70 via the second planet gears 90. It will be appreciated, however, that the output shaft 46 could be somewhat longer than that which is shown in FIGS. 2-4 and that the second sun gear 84 could be rotatably disposed on the output shaft 46. It will also be appreciated that another structure, such as the first sun gear 82 or the planet carrier 80, could include a shaft onto which the second sun gear 84 and/or the third sun gear 86 could be rotatably disposed. Teeth of the second sun gear 84 can be meshingly engaged to teeth of the second planet gear 90, which in turn can mesh with teeth of the second ring gear 98. Each of the second planet gears 90 can be coupled to an associated one of the first planet gears 88 for common rotation about an associated one of the carrier pins 106. In the example provided, each pair of first and second planet gears 88 and 90 are unitarily and integrally formed (e.g., compressed and sintered powdered metal) and may be collectively referred to as a first compound planet gear 120. The third sun gear 86 can be coupled to the second sun gear 84 for common rotation. In the particular example provided, the second and third sun gears 84 and 86 are unitarily and integrally formed (e.g., compressed and sintered powdered metal) and may be collectively referred to as a first compound sun gear 124. Teeth of the third sun gear 86 can be meshingly engaged to teeth of the fourth planet gear 94. Each of the third planet gears 92 can be coupled to an associated one of the fourth planet gears 94 for common rotation about an associated one of the carrier pins 106. In the example provided, each pair of third and fourth planet gears 92 and 94 are unitarily and integrally formed (e.g., compressed and sintered powdered metal) and may be collectively referred to as a second compound planet gear 128. Teeth of the third planet gears 92 can meshingly engage teeth of the third ring gear 100. If desired, a thrust washer TW1 can be disposed between the first and second compound gears 120 and 128.

Each of the first, second and third ring gears 96, 98 and 100 can have a plurality of locking teeth 130 that can be disposed about their outer circumferential surfaces.

The second gearset portion 72 can comprise a planet carrier 134, a sun gear 136, a plurality of planet gears 138 and a ring gear 140. The planet carrier 134 can comprise a carrier body 144 and a plurality of carrier pins 146. The carrier body 144 can comprise a rear plate member 148 and a front plate member 150, and the opposite ends of the carrier pins 146 can be fixedly mounted to the rear and front plate members 148 and 150 to axially space the rear plate member 148 apart from the front plate member 150. Each of the planet gears 138 can be rotatably received on an associated one of the carrier pins 146 and can be meshingly engaged with teeth of the sun gear 136 and teeth of the ring gear 140. The ring gear 140 can be rotatably received in the gear case 32.

The speed change mechanism 62 can comprise a movable member 160 and a speed selector switch assembly 162. In the example provided, the movable member 160 is an annular collar that is mounted concentrically about the first gearset portion 70 and which has internal teeth 166 that are configured to engage the locking teeth 130 on the first, second and third ring gears 96, 98 and 100. The speed selector switch assembly 162 can comprise a speed selector switch 170, one or more rails 172, a first biasing spring 174, a second biasing spring 176. The speed selector switch 170 can be slidably mounted to the housing assembly 12 and can be configured to receive a manual switching input from the user of the tool 10. The speed selector switch 170 can be translated between a first switch position, a second switch position and a third switch position in the particular example provided. The rails 172 can be fixedly coupled to the movable member 160 and slidably coupled to the speed selector switch 170 such that the movable member 160 can translate relative to the speed selector switch 170 and the first gearset portion 70. The first and second biasing springs 174 and 176 can bias the movable member 160 into a neutral position that corresponds to a position of the speed selector switch 170. The first and second biasing springs 174 and 176, however, permit the movable member 160 to be moved relative to the speed selector switch 170 in opposite axial directions.

Placement of the speed selector switch 170 in the first switch position positions the movable member 160 in a first position in which the internal teeth 166 of the movable member 160 are engaged with the locking teeth 130 of the first ring gear 96 such that the first gearset portion 70 operates in the first mode (i.e., a first overall speed reduction ratio). Movement of the speed selector switch 170 from the first switch position to the second switch position positions the movable member 160 in a second position in which the internal teeth 166 of the movable member 160 are engaged with the locking teeth 130 of the second ring gear 98 such that the first gearset portion 70 operates in the second mode (i.e., a second overall speed reduction ratio). Movement of the speed selector switch 170 from the second switch position to the third switch position positions the movable member 160 in a third position in which the internal teeth 166 of the movable member 160 are engaged with the locking teeth 130 of the third ring gear 100 such that the first gearset portion 70 operates in the third mode (i.e., a third overall speed reduction ratio).

If the internal teeth 166 of the movable member 160 are not aligned with the locking teeth of the second ring gear 98 or third ring gear 100 when the speed selector switch 170 is moved from the first switch position to the second switch position or from the second switch position to the third switch position, the first biasing spring 174 can compress to permit the speed selector switch 170 to move relative to the movable member 160. Similarly, if the internal teeth 166 of the movable member 160 are not aligned with the locking teeth of the second ring gear 98 or the first ring gear 96 when the speed selector switch is moved from the third switch position to the second switch position or from the second switch position to the first switch position, the second biasing spring 176 can compress to permit the speed selector switch 170 to move relative to the movable member 160. In this way, the user may complete the movement of the speed selector switch 170 (to a desired switch position) and the first and second biasing springs 174 and 176 can exert a force onto the movable member 160 to axially translate the movable member 160 (to thereby change the mode in which the first gearset portion 70 operates) when the internal teeth 166 are in alignment with the locking teeth 130 on the associated one of the first, second and third ring gears 96, 98 and 100.

The clutch assembly 20 can be a conventional clutch assembly that can be configured to limit the transmission of torque from the transmission assembly 18 to the output spindle 22. In the particular example provided, the clutch assembly 20 comprises a plurality of clutch pins 182, a clutch spring 186 and an adjustment nut 188 that is threadably mounted to a threaded member 190 that is non-rotatably but axially slidably mounted to the gear case 32. Each of the clutch pins 182 can be received through a corresponding pin hole 194 in the gear case 32. The clutch pins 182 can abut the ring gear 140 and can abut the clutch spring 186 on a side opposite the ring gear 140. The clutch spring 186 can be compressed between the clutch pins 182 and the adjustment nut 188 and can apply a force to the clutch pins 182 that resists rotation of the ring gear 140. The adjustment nut 188 is threaded to the threaded member 190 on the clutch housing 180 to permit the force that is exerted by the clutch spring 186 onto the clutch pins 182 to be selectively adjusted.

The output spindle 22 can be coupled to the planet carrier 134 for rotation therewith, but in the particular example provided, a conventional spindle lock assembly 198 is disposed between the planet carrier 134. As those of ordinary skill in the art will appreciate, the spindle lock assembly 198 is configured to permit the planet carrier 134 to drive the output spindle 22 and to inhibit rotation of the output spindle 22 that would tend to drive the planet carrier 134.

With reference to FIG. 4, positioning of the speed selector switch 170 (FIG. 3) in the third switch position positions the movable member 160 in engagement with the third ring gear 100 such that the third ring gear 100 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70. It will be further appreciated that because the third planet gears 92 are coupled to the fourth planet gears 94 for common rotation, the third planet gears 92 will drive the planet carrier 80 such that the first gearset portion 70 operates in fourth overall speed reduction ratio. It will be appreciated that any ring gears in the first gearset portion 70 that are non-rotatably coupled to the housing assembly 12 (i.e., via the movable member 160) are rotatable relative to the housing assembly 12. Accordingly, the first and second ring gears 96 and 98 are rotatable relative to the housing assembly 12 in this mode of operation.

With reference to FIG. 5, positioning of the speed selector switch 170 (FIG. 3) in the second switch position positions the movable member 160 in engagement with the second ring gear 98 such that the second ring gear 98 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. The second planet gears 90, which rotate with the first planet gears 88, will drive the planet carrier 80 such that the first gearset portion 70 operates in second overall speed reduction ratio. It will be appreciated, however, that rotation of the second planet gears 90 will also cause corresponding rotation of the first compound sun gear 124 and the second compound planet gear 128. Since the third ring gear 100 is permitted to rotate relative to the housing assembly 12, rotation of the first compound sun gear 124 and the second compound planet gear 128 will have only a minor effect on the efficiency of the first gearset portion 70.

With reference to FIG. 6, positioning of the speed selector switch 170 (FIG. 3) in the first switch position positions the movable member 160 in engagement with the first ring gear 96 such that the first ring gear 96 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88, which drives the planet carrier 80 such that the first gearset portion 70 operates in a first overall speed reduction ratio. Rotation of the first planet gears 88 will cause corresponding rotation of the second planet gears 90 and that rotation of the second planet gears 90 will also cause corresponding rotation of the first compound sun gear 124 and the second compound planet gear 128. Since the second and third ring gears 98 and 100 are permitted to rotate relative to the housing assembly 12, rotation of the second planet gear 90, the first compound sun gear 124 and the second compound planet gear 128 will have only a minor effect on the efficiency of the first gearset portion 70.

It will be appreciated that in all modes other than the first mode (in which the first planet gears 88 drive the planet carrier 80 such that the first gearset portion 70 operates in a first overall speed reduction ratio, the first gearset portion 70 operates such that at least one intermediate gear reduction is provided between the input sun gear 82 and the planet gears that drive the planet carrier 80 (i.e., the planet gears that are meshed with the ring gear that is non-rotatably coupled to the housing assembly 12) to thereby provide the first gearset portion 70 with an overall gear reduction ratio that is lower than the overall gear reduction ratio when the first gearset portion 70 is operated in the first mode.

With reference to FIG. 7, another tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10 a. The tool 10 a can be generally similar to the tool 10 of FIG. 1, except that the first gearset portion 70 a additionally comprises a fourth ring gear 200 that is disposed between the second and third ring gears 98 and 100, the second compound planet gear 128 is flipped in a front-to-back direction and the speed selector switch 170 is movable into a fourth switch position to cause the tool 10 a to operate in a fourth mode (i.e., a fourth overall speed reduction ratio). The fourth ring gear 200 has teeth that are meshed with the teeth of the fourth planet gears 94 and like the first, second and third ring gears 96, 98 and 100, locking teeth 130 are formed about the outer circumferential surface of the fourth ring gear 200. The speed selector switch 170 may be positioned in the first, second or third switch positions as is shown in FIGS. 8, 9 and 10, respectively, and the tool 10 a will operate as described above with the only difference being that the fourth ring gear 200 is rotatable relative to the housing assembly 12 when the first gearset portion 70 a is operated in these modes. Positioning of the speed selector switch 170 in the fourth switch position as shown in FIG. 7 positions the movable member 160 in engagement with the fourth ring gear 200 such that the fourth ring gear 200 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 a. Since the third sun gear 86 is coupled to the second sun gear 84 for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 a. The fourth planet gears 92 will drive the planet carrier 80 such that the first gearset portion 70 a operates in a fourth overall speed reduction ratio that is intermediate the second and third overall speed reduction ratios.

In FIG. 11, another tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10 b. The tool 10 b is generally similar to the tool 10 a of FIG. 7, except that the first gearset portion 70 b further comprises a fourth sun gear 250, a fifth sun gear 252, a fifth planet gear 254, a sixth planet gear 256, a fifth ring gear 258 and a sixth ring gear 260, and the speed selector switch 170 is movable into fifth and sixth switch position to cause the tool 10 b to operate in fifth and sixth modes, respectively. The fourth sun gear 250 can be axially spaced apart from the third sun gear 86 such that it is not directly coupled to the output shaft 46, the first sun gear 82, the first compound sun gear 124 or the first planet carrier 80. Teeth of the fourth sun gear 250 can be meshingly engaged to teeth of the third planet gears 92. The fourth sun gear 250 can be coupled to the fifth sun gear 252 for common rotation. In the particular example provided, the fourth and fifth sun gears 250 and 252 are unitarily and integrally formed (e.g., compressed and sintered powdered metal) and may be collectively referred to as a second compound sun gear 264. Teeth of the fifth sun gear 252 can be meshingly engaged to teeth of the fifth planet gear 254, which can be meshed with teeth of the fifth ring gear 258. Each of the fifth planet gears 254 can be coupled to an associated one of the sixth planet gears 256 for common rotation about an associated one of the carrier pins 106. In the example provided, each pair of fifth and sixth planet gears 254 and 256 are unitarily and integrally formed (e.g., compressed and sintered powdered metal) and may be collectively referred to as a third compound planet gear 266. Teeth of the sixth planet gears 256 can meshingly engage teeth of the sixth ring gear 260.

Positioning of the speed selector switch 170 in the sixth switch position positions the movable member 160 in engagement with the sixth ring gear 260 (as shown in FIG. 12) such that the sixth ring gear 260 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the third planet gears 92. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 b. As the third planet gears 92 are coupled to the fourth planet gears 94 for common rotation and as the teeth of the third planet gears 92 are meshingly engaged to the teeth of the fourth sun gear 250, rotation of the third planet gears 92 causes corresponding rotation of the fourth sun gear 250. It will be appreciated that since the pitch diameter of the third planet gears 92 is smaller than the pitch diameter of the third planet gears 92, and since the pitch diameter of the fourth sun gear 250 is larger than the pitch diameter of the third sun gear 86, the second compound planet gear 128 cooperates to produce a third intermediate gear reduction within the first gearset portion 70 b. Since the fifth sun gear 252 is coupled to the fourth sun gear for common rotation, and since the teeth of the fifth planet gears 254 are meshed with the teeth of the fifth sun gear 252, rotation of the fourth sun gear 250 causes corresponding rotation of the fifth planet gears 254. It will be appreciated that since the pitch diameter of the fifth sun gear 252 is smaller than the pitch diameter of the fourth sun gear 250, and since the pitch diameter of the fifth planet gears 254 is larger than the pitch diameter of the third planet gears 92, the second compound sun gear 264 cooperates to produce a fourth intermediate gear reduction within the first gearset portion 70 b. Because the sixth planet gears 256 are coupled to the fifth planet gears 254 for common rotation, the sixth planet gears 256 will drive the planet carrier 80 such that the first gearset portion 70 b operates in sixth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the fifth switch position positions the movable member 160 in engagement with the fifth ring gear 258 (as shown in FIG. 13) such that the fifth ring gear 258 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 b. As the third planet gears 92 are coupled to the fourth planet gears 94 for common rotation and as the teeth of the third planet gears 92 are meshingly engaged to the teeth of the fourth sun gear 250, rotation of the third planet gears 92 causes corresponding rotation of the fourth sun gear 250. It will be appreciated that since the pitch diameter of the third planet gears 92 is smaller than the pitch diameter of the fourth planet gears 94, and since the pitch diameter of the fourth sun gear 250 is larger than the pitch diameter of the third sun gear 86, the second compound planet gear 128 cooperates to produce a third intermediate gear reduction within the first gearset portion 70 b. Since the fifth sun gear 252 is coupled to the fourth sun gear for common rotation, and since the teeth of the fifth planet gears 254 are meshed with the teeth of the fifth sun gear 252, rotation of the fourth sun gear 250 causes corresponding rotation of the fifth planet gears 254. Rotation of the fifth planet gears 254 drives the planet carrier 80 such that the first gearset portion 70 b operates in fifth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a fourth switch position positions the movable member 160 in engagement with the third ring gear 100 (as shown in FIG. 14) such that the third ring gear 100 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the third planet gears 92 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 b. As the third planet gears 92 are coupled to the fourth planet gears 94 for common rotation, the third planet gears 92 drive the planet carrier 80 such that the first gearset portion 70 b operates in a fourth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a third switch position positions the movable member 160 in engagement with the fourth ring gear 200 (as shown in FIG. 15) such that the fourth ring gear 200 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94, which drive the planet carrier 80 such that the first gearset portion 70 b operates in a third overall speed reduction ratio.

Positioning of the speed selector switch 170 in the second switch position positions the movable member 160 in engagement with the second ring gear 98 (as shown in FIG. 16) such that the second ring gear 98 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation, rotation of the second planet gears 90 drives the planet carrier 80 such that the first gearset portion 70 b operates in a second overall speed reduction ratio.

Positioning of the speed selector switch 170 in the first switch position positions the movable member 160 in engagement with the first ring gear 96 (as shown in FIG. 17) such that the first ring gear 96 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88, which drive the planet carrier 80 such that the first gearset portion 70 b operates in a first overall speed reduction ratio.

The examples of FIGS. 11A and 11B are generally similar to the example of FIG. 11 except that the first sun gear 82 (FIG. 11) has been omitted and that either the first compound sun gear 124 or the second compound sun gear 264 is coupled to the output shaft 46 for rotation therewith as shown in FIGS. 11A and 11B, respectively.

With regard to the example of FIG. 11A, the speed selector switch 170 can be positioned in the sixth switch position, which positions the movable member 160 in engagement with the ring gear 260 such that the ring gear 260 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the first compound sun gear 124. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 92 due to the meshing engagement of the teeth of the planet gears 92 with the teeth of the sun gear 86. As the planet gears 92 are coupled to the planet gears 94 for common rotation and as the teeth of the planet gears 92 are meshingly engaged to the teeth of the sun gear 250, rotation of the planet gears 92 causes corresponding rotation of the sun gear 250. It will be appreciated that since the pitch diameter of the planet gears 92 is smaller than the pitch diameter of the planet gears 92, and since the pitch diameter of the sun gear 250 is larger than the pitch diameter of the sun gear 86, the second compound planet gear 128 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the sun gear 252 is coupled to the sun gear for common rotation, and since the teeth of the planet gears 254 are meshed with the teeth of the sun gear 252, rotation of the sun gear 250 causes corresponding rotation of the planet gears 254. It will be appreciated that since the pitch diameter of the sun gear 252 is smaller than the pitch diameter of the sun gear 250, and since the pitch diameter of the planet gears 254 is larger than the pitch diameter of the planet gears 92, the second compound sun gear 264 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 b. Because the planet gears 256 are coupled to the planet gears 254 for common rotation, the planet gears 256 will drive the planet carrier 80 such that the first gearset portion 70 b operates in sixth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the fifth switch position positions the movable member 160 in engagement with the ring gear 258 such that the ring gear 258 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the first compound sun gear 124. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 92 due to the meshing engagement of the teeth of the planet gears 92 with the teeth of the sun gear 86. As the planet gears 92 are coupled to the planet gears 94 for common rotation and as the teeth of the planet gears 92 are meshingly engaged to the teeth of the sun gear 250, rotation of the planet gears 92 causes corresponding rotation of the sun gear 250. It will be appreciated that since the pitch diameter of the planet gears 92 is smaller than the pitch diameter of the planet gears 92, and since the pitch diameter of the sun gear 250 is larger than the pitch diameter of the sun gear 86, the second compound planet gear 128 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 b. Since the sun gear 252 is coupled to the sun gear for common rotation, and since the teeth of the planet gears 254 are meshed with the teeth of the sun gear 252, rotation of the sun gear 250 causes corresponding rotation of the planet gears 254. Rotation of the planet gears 254 drives the planet carrier 80 such that the first gearset portion 70 b operates in fifth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a fourth switch position positions the movable member 160 in engagement with the ring gear 100 such that the ring gear 100 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the first compound sun gear 124. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 92 due to the meshing engagement of the teeth of the planet gears 92 with the teeth of the sun gear 86. As the planet gears 92 are coupled to the planet gears 94, the planet gears 94 drive the planet carrier 80 such that the first gearset portion 70 b operates in a fourth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a third switch position positions the movable member 160 in engagement with the ring gear 200 such that the ring gear 200 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the first compound sun gear 124. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 92 due to the meshing engagement of the teeth of the planet gears 92 with the teeth of the sun gear 86. The planet gears 92 drive the planet carrier 80 such that the first gearset portion 70 b operates in a third overall speed reduction ratio.

Positioning of the speed selector switch 170 in the second switch position positions the movable member 160 in engagement with the ring gear 98 such that the ring gear 98 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the first compound sun gear 124. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 90 due to the meshing engagement of the teeth of the planet gears 90 with the teeth of the sun gear 84. The planet gears 90 drive the planet carrier 80 such that the first gearset portion 70 b operates in a second overall speed reduction ratio.

Positioning of the speed selector switch 170 in the first switch position positions the movable member 160 in engagement with the ring gear 96 (as shown in FIG. 17) such that the ring gear 96 is nonrotatably coupled to the housing assembly 12. Rotation of the first compound sun gear 124 causes corresponding rotation of the planet gears 90 due to the meshing engagement of the teeth of the planet gears 90 with the teeth of the sun gear 84. As the planet gears 88 are coupled to the planet gears 90 for rotation therewith, the planet gears 88 drive the planet carrier 80 such that the first gearset portion 70 b operates in a first overall speed reduction ratio.

With regard to the example of FIG. 11B, the speed selector switch 170 can be positioned in the sixth switch position, which positions the movable member 160 in engagement with the ring gear 260 such that the ring gear 260 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 254 due to the meshing engagement of the teeth of the planet gears 254 with the teeth of the sun gear 252. As the planet gears 254 are coupled to the planet gears 256 for common rotation and as the teeth of the planet gears 254 are meshingly engaged to the teeth of the sun gear 252, the planet gears 256 will drive the planet carrier 80 such that the first gearset portion 70 b operates in sixth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the fifth switch position positions the movable member 160 in engagement with the ring gear 258 such that the ring gear 258 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 254 due to the meshing engagement of the teeth of the planet gears 254 with the teeth of the sun gear 252. Rotation of the planet gears 254 drives the planet carrier 80 such that the first gearset portion 70 b operates in fifth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a fourth switch position positions the movable member 160 in engagement with the ring gear 100 such that the ring gear 100 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 94 due to the meshing engagement of the teeth of the planet gears 94 with the teeth of the sun gear 250. Rotation of the planet gears 94 drives the planet carrier 80 such that the first gearset portion 70 b operates in fourth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a third switch position positions the movable member 160 in engagement with the ring gear 200 such that the ring gear 200 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 94 due to the meshing engagement of the teeth of the planet gears 94 with the teeth of the sun gear 250. Since the planet gears 92 are coupled for rotation with the planet gears 94 for common rotation, the planet gears 92 drive the planet carrier 80 such that the first gearset portion 70 b operates in a third overall speed reduction ratio.

Positioning of the speed selector switch 170 in the second switch position positions the movable member 160 in engagement with the ring gear 98 such that the ring gear 98 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 94 due to the meshing engagement of the teeth of the planet gears 94 with the teeth of the sun gear 250. Since the planet gears 92 are coupled for rotation with the planet gears 94 for common rotation, the planet gears 92 drive sun gear 86. Since the sun gear 84 is coupled for rotation with the sun gear 86, rotation of the sun gear 86 causes corresponding rotation of the planet gears 90 (due to meshing engagement between the planet gears 90 and the sun gear 84). Rotation of the planet gears 90 drives the planet carrier 80 such that the first gearset portion 70 b operates in a second overall speed reduction ratio.

Positioning of the speed selector switch 170 in the first switch position positions the movable member 160 in engagement with the ring gear 96 (as shown in FIG. 17) such that the ring gear 96 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the second compound sun gear 264. Rotation of the second compound sun gear 264 causes corresponding rotation of the planet gears 94 due to the meshing engagement of the teeth of the planet gears 94 with the teeth of the sun gear 250. Since the planet gears 92 are coupled for rotation with the planet gears 94 for common rotation, the planet gears 92 drive sun gear 86. Since the sun gear 84 is coupled for rotation with the sun gear 86, rotation of the sun gear 86 causes corresponding rotation of the planet gears 90 (due to meshing engagement between the planet gears 90 and the sun gear 84). As the planet gears 88 are coupled to the planet gears 90 for rotation therewith, rotation of the planet gears drives the planet gears 88, which drive the planet carrier 80 such that the first gearset portion 70 b operates in a first overall speed reduction ratio.

In FIG. 18, another tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10 c. The tool 10 c is generally similar to the tool 10 b of FIG. 11, except that the first gearset portion 70 b is configured to output rotary power directly to the output spindle 22 c. In this regard, the planet carrier 80 c is modified to work directly with the spindle lock assembly 198 to transmit rotary power to the output spindle 22 c.

In FIG. 19, a further tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10 d. The tool 10 d is generally similar to the tool 10 a of FIG. 7, except for the configuration of the first gearset portion and the speed selector switch. More specifically, the first gearset portion 70 d is configured such that the first or input sun gear 82 is positioned proximate the front plate member 112 d, the first ring gear has been omitted, and the speed selector switch 170 is selectively positionable in the second and third switch positions.

Positioning of the speed selector switch 170 in the third switch position (shown in FIG. 20) positions the movable member 160 in engagement with the third ring gear 100 (closest to the motor assembly 14 d in this example) such that the third ring gear 100 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 d is transmitted from the output shaft 46 d to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 d. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 d. It will be further appreciated that because the third planet gears 92 are coupled to the fourth planet gears 94 for common rotation, the third planet gears 92 will drive the planet carrier 80 such that the first gearset portion 70 d operates in a fourth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the third switch position (shown in FIG. 21) positions the movable member 160 in engagement with the fourth ring gear 200 such that the fourth ring gear 200 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. As the second planet gears 90 are coupled to the first planet gears 88 for common rotation and as the teeth of the second planet gears 90 are meshingly engaged to the teeth of the second sun gear 84, rotation of the second planet gears 90 causes corresponding rotation of the second sun gear 84. It will be appreciated that since the pitch diameter of the second planet gears 90 is smaller than the pitch diameter of the first planet gears 88, and since the pitch diameter of the second sun gear 84 is larger than the pitch diameter of the first sun gear 82, the first compound planet gear 120 cooperates to produce a first intermediate gear reduction within the first gearset portion 70 d. Since the third sun gear 86 is coupled to the second sun gear for common rotation, and since the teeth of the fourth planet gears 94 are meshed with the teeth of the third sun gear 86, rotation of the second sun gear 84 causes corresponding rotation of the fourth planet gears 94. It will be appreciated that since the pitch diameter of the third sun gear 86 is smaller than the pitch diameter of the second sun gear 84, and since the pitch diameter of the fourth planet gears 94 is larger than the pitch diameter of the second planet gears 90, the first compound sun gear 124 cooperates to produce a second intermediate gear reduction within the first gearset portion 70 d. The fourth planet gears 94 will drive the planet carrier 80 such that the first gearset portion 70 d operates in third overall speed reduction ratio that is intermediate the second and fourth overall speed reduction ratios.

Positioning of the speed selector switch 170 in the second switch position (shown in FIG. 22) positions the movable member 160 in engagement with the second ring gear 98 such that the second ring gear 98 is nonrotatably coupled to the housing assembly 12. Rotary power output from the motor assembly 14 is transmitted from the output shaft 46 to the input sun gear 82. Rotation of the input sun gear 82 causes corresponding rotation of the first planet gears 88 due to the meshing engagement of the teeth of the first planet gears 88 with the teeth of the input sun gear 82. The second planet gears 90 will drive the planet carrier 80 such that the first gearset portion 70 d operates in second overall speed reduction ratio.

With reference to FIG. 23, another tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 10 e. The tool 10 e is generally similar to the tool 10 d of FIG. 19, except that the fourth ring gear has been omitted. Accordingly, the tool 10 e has a first gearset portion 70 e that is selectively operable in two overall speed reduction ratios.

It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein, even if not specifically shown or described, so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims. 

What is claimed is:
 1. A power tool comprising: a housing assembly defining a handle; a motor assembly received in the housing assembly and having an output shaft; a trigger assembly coupled to the housing assembly and configured for use in actuating the motor assembly; a spindle; and a transmission assembly transmitting rotary power between the motor assembly and the spindle, the transmission assembly comprising a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier, wherein the planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.
 2. The tool of claim 1, wherein the transmission assembly includes a member that is movable between a first position and a second position, wherein the planetary stage operates in the first mode when the member is positioned in the first position and wherein the planetary stage operates in the second mode when the member is positioned in the second position.
 3. The tool of claim 2, wherein the planetary stage further comprises a plurality of ring gears and wherein the member engages a first one of the plurality of ring gears when the member is positioned in the first position and wherein the member engages a second one of the plurality of ring gears when the member is positioned in the second position.
 4. The tool of claim 3, wherein engagement of the member to any one of the plurality of ring gears nonrotatably couples that ring gear to the housing assembly.
 5. The tool of claim 2, wherein the transmission assembly further comprises a speed selector switch and wherein the member is resiliently coupled to the speed selector switch.
 6. The tool of claim 5, wherein the member is biased into a neutral position and is movable relative to the speed selector switch in opposite axial directions.
 7. The tool of claim 1, wherein the planetary stage provides at least three different overall gear reduction ratios.
 8. The tool of claim 7, wherein the planetary stage is selectively operable in a third mode in which the first intermediate gear reduction and a second intermediate gear reduction are produced within the planetary stage.
 9. The tool of claim 8, wherein the planetary stage provides at least four different overall gear reduction ratios.
 10. The tool of claim 9, wherein the planetary stage is selectively operable in a fourth mode in which the first intermediate gear reduction, the second intermediate gear reduction and a third intermediate gear reduction are produced within the planetary stage.
 11. The tool of claim 1, further comprising a clutch for limiting torque transmitted from the transmission assembly to the spindle.
 12. The tool of claim 1, wherein the input sun gear is directly driven by the output shaft of the motor assembly.
 13. A power tool comprising: a housing assembly defining a handle; a motor assembly received in the housing assembly and having an output shaft; a trigger assembly coupled to the housing assembly and configured for use in actuating the motor assembly; a spindle; and a transmission assembly transmitting rotary power between the motor assembly and the spindle, the transmission assembly comprising a gearset portion with a planet carrier, an input sun gear, and at least one compound planet gear supported for rotation by the planet carrier, the planet carrier being an output member of the gearset portion, each compound planet gear having first and second planet gears that are coupled to one another for common rotation, wherein the first planet gear has a pitch diameter that is different from a pitch diameter of the second planet gear, wherein the gearset portion is operable in a first mode which provides a first gear reduction ratio and a second mode that provides a second gear reduction ratio that is different than the first gear reduction ratio, and wherein in the second mode at least one intermediate gear reduction is provided within an axial length of the planet carrier.
 14. The tool of claim 13, wherein the transmission assembly includes a member that is movable between a first position and a second position, wherein the planetary stage operates in the first mode when the member is positioned in the first position and wherein the planetary stage operates in the second mode when the member is positioned in the second position.
 15. The tool of claim 14, wherein the planetary stage further comprises a plurality of ring gears and wherein the member engages a first one of the plurality of ring gears when the member is positioned in the first position and wherein the member engages a second one of the plurality of ring gears when the member is positioned in the second position.
 16. The tool of claim 15, wherein engagement of the member to any one of the plurality of ring gears nonrotatably couples that ring gear to the housing assembly.
 17. The tool of claim 14, wherein the transmission assembly further comprises a speed selector switch and wherein the member is resiliently coupled to the speed selector switch.
 18. The tool of claim 17, wherein the member is biased into a neutral position wherein the member is biased into a neutral position and is movable relative to the speed selector switch in opposite axial directions.
 19. A power tool comprising: a housing assembly defining a handle; a motor assembly received in the housing assembly and having an output shaft; a trigger assembly coupled to the housing assembly and configured for use in actuating the motor assembly; a spindle; and a transmission assembly transmitting rotary power between the motor assembly and the spindle, the transmission assembly comprising a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier, wherein the planetary stage performs a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.
 20. A power tool comprising: a housing assembly defining a handle; a motor assembly received in the housing assembly and having an output shaft; a trigger assembly coupled to the housing assembly and configured for use in actuating the motor assembly; a spindle; and a transmission assembly transmitting rotary power between the motor assembly and the spindle, the transmission assembly comprising a gearset portion with a planet carrier, an input sun gear, a compound sun gear, a first planet gear, a second planet gear, a third planet gear, and a plurality of ring gears, the compound sun gear comprising a first intermediate sun gear and a second intermediate sun gear that are coupled to one another for common rotation, the first, second and third planet gears being rotatably disposed on the planet carrier, the second planet gear being coupled to the first planet gear for rotation therewith, the first planet gear being meshingly engaged with the input sun gear, the second planet gear being meshingly engaged with the first intermediate sun gear, and the third planet gear being meshingly engaged with the second intermediate sun gear, the plurality of ring gears comprising a first ring gear, which is meshingly engaged to one of the first, second and third planet gears, and a second ring gear that is meshingly engaged to a different one of the first, second and third planet gears, wherein the gearset portion is operable in a first mode in which the first ring gear is maintained in a non-rotating condition relative to the housing assembly and the second ring gear is rotatable relative to the housing assembly, and wherein the gearset portion is operable in a second mode in which the second ring gear is maintained in a non-rotating condition relative to the housing assembly and the first ring gear is rotatable relative to the housing assembly. 